Highly-conductive PEDOT:PSS hydrogel framework based hybrid fiber with high volumetric capacitance and excellent rate capability

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Fiber supercapacitors (FSCs) are attractive energy storage devices for wearable and portable electronics. However, it still remains a great challenge to achieve high volumetric specific capacitance without sacrificing the rate capability of FSC. Here, we demonstrate a novel hierarchically nanostructured hybrid fiber with thin polyaniline (PANI) layer anchored on the highly-conductive poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) hydrogel framework as electrodes for FSCs. The hybrid fiber was prepared via hydrothermal assembly of a commercial PEDOT:PSS dispersion followed by acid treatment and in-situ chemical polymerization of aniline. The incorporation of highly-electroactive PANI boosts the whole capacitance of hybrid fiber; the robust PEDOT hydrogel framework provides abundant ions diffusion channels and rapid electron transfer pathways, improving the utilization efficiency and the kinetics of pseudocapacitance reaction of PANI. Attributed to the synergistic effect, the PEDOT/PANI hybrid fiber in FSC exhibits high volumetric/areal specific capacitance (554.1 F cm−3 or 740.0 mF cm−2 at 5 A cm−3), excellent rate performance and good electrochemical stability. The flexible FSC device delivers a high volumetric energy density of 11.9 mWh cm−3 at 981.4 mW cm−3 and areal energy density of 15.8 μWh cm−2 at 1310.5 μW cm−2, outperforming most of the reported counterparts. The well-designed PEDOT/PANI hybrid fiber based FSC hold a great potential for powering the next-generation wearable and portable electronics.